Of the 1.2 million Americans living with HIV/AIDS, over half experience HIV-associated neurocognitive impairment. Marijuana is the most commonly abused drug among HIV+ persons; over a third have used marijuana in the past year, with >25% reporting no other drug use. Although chronic marijuana use also alters brain functioning and can produce neurocognitive impairment, few studies have investigated interactions between marijuana and HIV infection on brain functioning. It is hypothesized that marijuana's effect on brain functioning will be more pronounced among HIV+ individuals due to their already limited cognitive resources. The proposed project integrates training and research plans that are designed to develop the applicant's expertise in neurocognitive assessment, brain circuitry relevant to HIV infection and addiction, functional magnetic resonance imaging (fMRI) design and data analysis, and advanced statistical analysis. This research plan will allow her to implement and refine newly developed skills in these areas. Specifically, the applicant seeks to integrate cognitive and neuroscience techniques into her patient-oriented research. The proposed project will provide her with mentored training in (1) assessment of neurocognitive impairment associated with HIV infection and drug abuse, (2) the application of fMRI technology to clinical research, and (3) longitudinal analyses using repeated measures and multilevel designs. The training plan includes coursework and workshops, one-on-one mentorship, participation in seminars, directed readings, and attendance at national and international conferences. In Study 1 (Neurocognitive Assessment), 75 HIV+ persons stratified by marijuana use will complete a battery of neurocognitive and experimental decision-making tasks. The goal is to identify patterns of neurocognitive functioning associated with co-occurring HIV infection and marijuana use (Aim 1), and to test whether these relationships are moderated by HIV disease progression (Aim 2). Study 2 (fMRI Analysis) utilizes fMRI to examine brain activation patterns as a function of marijuana use during a decision-making task with the aim of elucidating neural mechanisms underlying cognitive processes altered by HIV and marijuana (Aim 3). This integration of research methodologies is expected to inform future research in this understudied field. Furthermore, at the culmination of this fellowship, the applicant will have a specialized skll set and be well prepared to begin the next phase of her training, in which she intends to gain further expertise in the application of fMRI technology to patient-oriented research in HIV+ persons.